Retrospective determination of fallout radionuclides and 236U/238U, 233U/236U and 240Pu/239Pu atom ratios on air filters from Vienna and Salzburg, Austria.

137Cs and 241Pu (via 241Am) concentrations were measured γ-spectrometrically on air filters from the early 1960s (mainly from 1964-66) from Vienna, Austria, and an alpine station in Salzburg, Austria. Accelerator mass spectrometry (AMS) was used to determine 240Pu/239Pu, 236U/238U and 233U/236U atom ratios as well as 236U, 239Pu and 240Pu atom concentrations. The maximum 236U/238U atom ratio of these unique undisturbed global fallout samples was (1.19 ± 0.31) × 10-5 in spring 1964. The 233U/236U atom ratios were found within (0.15-0.49) × 10-2 and indicate that the weapons tests of the early 1960s can be excluded as 233U source. The 236U/239Pu atom ratios were calculated in the range of 0.22-0.48.

European roe deer antlers as an environmental archive for fallout (236)U and (239)Pu.

Anthropogenic (236)U and (239)Pu were measured in European roe deer antlers hunted between 1955 and 1977 which covers and extends beyond the period of intensive nuclear weapons testing (1954-1962). The antlers were hunting trophies, and hence the hunting area, the year of shooting and the approximate age of each animal is given. Uranium and plutonium are known to deposit in skeletal tissue. Since antler histology is similar to bone, both elements were expected in antlers. Furthermore, roe deer shed their antlers annually, and hence antlers may provide a time-resolved environmental archive for fallout radionuclides. The radiochemical procedure is based on a Pu separation step by anion exchange (Dowex 1 × 8) and a subsequent U purification by extraction chromatography using UTEVA(®). The samples were measured by Accelerator Mass Spectrometry at the VERA facility (University of Vienna). In addition to the (236)U and (239)Pu concentrations, the (240)Pu/(239)Pu isotopic ratios were determined with a mean value of 0.172 ± 0.023 which is in agreement with the ratio of global fallout (∼0.18). Rather high (236)U/(238)U ratios of the order of 10(-6) were observed. These measured ratios, where the (236)U arises only from global fallout, have implications for the use of the (236)U/(238)U ratio as a fingerprint for nuclear accidents or releases from nuclear facilities. Our investigations have shown the potential to use antlers as a temporally resolved archive for the uptake of actinides from the environment.

236U/238U and 240Pu/239Pu isotopic ratios in small (2 L) sea and river water samples.

Accelerator Mass Spectrometry (AMS) and alpha spectrometry were used to determine uranium ((236)U, (238)U, (234)U) and plutonium isotopes ((239)Pu, (240)Pu) in sea and river water samples. Plutonium was separated by Dowex(®) 1 × 8 resin and UTEVA(®) resin was used for uranium purification. The measured (236)U/(238)U isotopic ratios for surface water from the Atlantic Ocean, the Pacific Ocean and the Black Sea were in the order of 10(-9), while values for river water were in the order of 10(-8). These contaminations may be attributed to global fallout. A sample of the reference material IAEA-443, collected from the Irish Sea, showed, in accordance to the reference value, a ratio that was 10(3) times higher due to effluents from the reprocessing plant at Sellafield. These results underline the good suitability of (236)U/(238)U as a tracer for hydrology and oceanography, and show that relatively small water samples are sufficient for the determination of (236)U by AMS, which is not the case for plutonium with present techniques. The plutonium concentrations in our water samples could only be measured with large uncertainties and were in the order of 10(-3) mBq/L (with the exception of the Irish Sea sample).

Depth profile of ²³6U/²³8U in soil samples in La Palma, Canary Islands.

The vertical distribution of the (236)U/(238)U isotopic ratio was investigated in soil samples from three different locations on La Palma (one of the seven Canary Islands, Spain). Additionally the (240)Pu/(239)Pu atomic ratio, as it is a well establish tool for the source identification, was determined. The radiochemical procedure consisted of a U separation step by extraction chromatography using UTEVA Resin (Eichrom Technologies, Inc.). Afterwards Pu was separated from Th and Np by anion exchange using Dowex 1 x 2 (Dow Chemical Co.). Furthermore a new chemical procedure with tandem columns to separate Pu and U from the matrix was tested. For the determination of the uranium and plutonium isotopes by alpha spectrometry thin sources were prepared by microprecipitation techniques. Additionally these fractions separated from the soil samples were measured by Accelerator Mass Spectrometry (AMS) to get information on the isotopic ratios (236)U/(238)U, (240)Pu/(239)Pu and (236)U/(239)Pu, respectively. The (236)U concentrations [atoms/g] in each surface layer (∼2 cm) were surprisingly high compared to deeper layers where values around two orders of magnitude smaller were found. Since the isotopic ratio (240)Pu/(239)Pu indicated a global fallout signature we assume the same origin as the probable source for (236)U. Our measured (236)U/(239)Pu value of around 0.2 is within the expected range for this contamination source.

Determination of U, Pu and Am isotopes in Irish Sea sediment by a combination of AMS and radiometric methods.

Samples from a marine sediment core from the Irish Sea (54.416 N, 3.563 W) were analyzed for the isotopic composition of uranium, plutonium and americium by a combination of radiometric methods and AMS. The radiochemical procedure consisted of a Pu separation step by anion exchange, subsequent U separation by extraction chromatography using UTEVA® and finally Am separation with TRU® Resin. Additionally to radiometric determination of these isotopes by alpha spectrometry, the separated samples were also used for the determination of (236)U/(238)U and plutonium isotope ratios by Accelerator Mass Spectrometry (AMS) at the VERA facility.

The first use of (236)U in the general environment and near a shutdown nuclear power plant.

We present a first effort to investigate (236)U in the environment near a shutdown nuclear power plant far away from highly contaminated sites, by using accelerator mass spectrometry. The detection limit of about 1pg (236)U allowed us to identify a minimal increase of the (236)U/(238)U isotopic ratio correlated to a peak of (137)Cs in river sediments downstream of the nuclear power plant, and to detect anthropogenic (236)U also upstream, where it is probably not related to the power plant but to global fallout. The (236)U content shoved variations of the (236)U/(238)U isotopic ratio in relation to the chemical-physical characteristics of the sediments. This demonstrates the potential of (236)U as an environmental tracer, and as an indicator for releases from nuclear facilities.